1. Field of the Invention
The present invention relates to a method for processing a surface of light-transmitting-glass and to light-transmitting glass subjected to surface processing with the method, and more particularly relates to a surface processing method for suppressing the occurrence of specular reflections at the surface of light-transmitting glass and to light-transmitting glass processed by the said method, in other words the said glass subjected to surface processing with the method.
2. Description of the Prior Art
At present, there is continuously increasing concern from society about environmental problems, and the use of energy referred to as “natural energy” or “renewable energy” such as hydroelectric power, wind power, geothermal power, wave power, and sunlight which have a low environmental load is attracting interest.
As part of the use of such natural energy, photovoltaic power generation so called solar power generation in which power generation is performed by using solar energy is extensively used today, and photovoltaic modules used in photovoltaic power generation are becoming more widespread.
These photovoltaic modules have a construction in which a required number of photovoltaic cells are connected in series or in parallel and arranged side-by-side then covered by a cover glass such as tempered glass, to form a package.
Accordingly, in cases where the cover glass has a flat surface, unpleasant glare is experienced due to reflected light that is reflected at the surface getting into people's field of vision. Therefore, from the viewpoint of taking into consideration nearby residents, and from the viewpoint of safety in the vicinity of facilities such as ports, airports, roads, etc., photovoltaic modules endowed with antiglare specifications by virtue of the cover glass being subjected to antiglare treatment are becoming widespread.
As examples of such antiglare treatment for the cover glass of a photovoltaic module, a number of technologies designed to reduce glare have been proposed, such as a technology in which reflected light is diffused by attaching a light-diffusing sheet having indentations and protrusions formed thereon to the surface of a cover glass, thereby endowing the cover glass with antiglare properties (Japanese Unexamined Patent Application Publication No. 2001-189479), a technology in which diffuse reflection is generated by forming indentations and protrusions directly in the surface of a cover glass (Japanese Unexamined Patent Application Publication No. HEI 11-298030), or a technology in which the concentration of reflected light in a certain direction is prevented by forming multiple parallel grooves in the surface of a cover glass (Japanese Unexamined Patent Application Publication No. 2003-188399).
The cause of the glare experienced from a cover glass having a flat surface that is not subjected to antiglare treatment is that the reflections occurring at the flat surface of the cover glass are specular reflections as shown in FIG. 6A.
In other words, because specularly reflected light is reflected so as to be concentrated in a certain direction in the form of a collimated beam, like sunlight, unpleasant glare is experienced due to the reflected light getting into someone's field of vision in a concentrated manner.
Therefore, in cases where a light-diffusing sheet having indentations and protrusions formed in the surface thereof is bonded to the surface of a protective cover to diffuse the reflected light as disclosed in the above-cited '479 patent document, or in cases where indentations and protrusions or grooves are directly formed in the surface of a protective cover to cause the reflected light to be diffused, as disclosed in the above-cited '030 and '399 patent documents, because it is possible to avoid concentration of the reflected light in a certain direction as shown in FIG. 6B, the glare experienced even in cases where part of the reflected light gets into the field of vision is considerably reduced, and as a result, it is possible to endow the cover glass with an effective antiglare effect by any of these methods.
However, in either case, namely, the case in which the light-diffusing sheet is bonded to the surface of the cover glass as described in the above-cited '479 patent document, or the case in which indentations and protrusions are directly formed in the surface of the cover glass as disclosed in the '030 and '399 patent documents, with a photovoltaic module provided with a cover glass that is subjected to such antiglare treatment, a decrease in electricity generating efficiency is found as compared with a photovoltaic module provided with an untreated cover glass on which antiglare treatment is not performed.
Such a reduction in the amount of generated power is considered to occur because the amount of light incident on the photovoltaic cells provided in a layer underneath is reduced since the amount of light that passes through the cover glass is reduced by subjecting the cover glass to the above-described antiglare treatment, and electricity generating performance which is an essential requirement of photovoltaic modules has been sacrificed at the expense of adding functions that take into consideration the nearby residents etc., namely, antiglare properties.
The above description has been given by taking the cover glass of a photovoltaic module as an example of an article subjected to antiglare treatment; however, the decrease in performance due to a reduction in the amount of transmitted light as a result of performing the antiglare treatment as described above is a problem that occurs not only with the cover glasses of photovoltaic modules, but also, in a similar manner, with light-transmitting glass subjected to antiglare treatment which is provided in various other types of devices and apparatuses, for example, the cover glasses of water heaters using solar heat, transparent panels used in greenhouses etc. for agricultural and horticultural uses, and so forth.
Thus, the present invention has been conceived to eliminate the deficiencies in the conventional technologies described above, and an object thereof is to provide a light-transmitting glass surface processing method that not only avoids a reduction in the amount of light passing through light-transmitting glass, but conversely, increases it, while at the same time endowing the light-transmitting glass with antiglare properties, as well as to provide light-transmitting glass provided with antiglare properties and high light-transmitting properties which are achieved by surface processing with the method.